President Trump, Vice President Mike Pence and multiple members of the Trump family have all campaigned in Pennsylvania's 18th Congressional District near Pittsburgh. Yet Democrats there insist tomorrow's special House election is not a referendum on Trump's presidency. As NPR's Scott Detrow reports, the party believes focusing on local issues is the way it can pull off what would be a major upset.

SCOTT DETROW, BYLINE: Democrat Conor Lamb is getting pretty well-known to the people in Pennsylvania's 18th District. When he knocks on doors...

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CONOR LAMB: A lot of them say, look; it's really nice to meet you, but I am getting a little tired of seeing your face during every commercial break.

DETROW: They're seeing a lot of it. The Lamb campaign is airing a ton of ads. And outside Republican groups are airing even more, trying to tie Lamb to House Minority Leader Nancy Pelosi and the National Democratic Party. But polls show a close race.

PAM SNYDER: Well, I think Lamb is a conservative Democrat. And I think that's what I like about him. His views and my views are very much alike.

DETROW: Pam Snyder is a Democratic state representative in the southern half of the 18th. It's a conservative, rural, pro-Trump, pro-natural gas and coal stretch where national Democrats usually don't do too well. Snyder says Lamb is holding his own in a county where Trump broke nearly 70 percent of the vote.

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CECIL ROBERTS: If you want more jobs, protect your job, you should vote for Conor.

DETROW: Miners don't have much good to say about Democrats in Washington these days. But Cecil Roberts, the president of the United Mine Workers of America, tore down the house Sunday stumping for Lamb.

DETROW: This support from labor isn't just about Lamb. The Republican in the race, Rick Saccone, has a long anti-union voting record in Harrisburg, so many labor voters like Dan Miller are ready to support Lamb. Miller backed Trump in 2016.

DAN MILLER: I want a change in America, and he's starting change. But I'd like to see a lot more toward the coal mines and the workers and our industries coming back to America. Put our people back to work.

DETROW: So Trump was up here last night. And he was saying, if you like me, vote for Rick Saccone.

MILLER: No way. No. You know, you can differ from somebody. And I feel that Saccone has never done anything for the working man. He's anti-union. He's for right-to-work.

DETROW: With these dynamics at play, Saccone is hugging Trump as tight as he can. Saccone even went after the media at a Saturday rally with the president.

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RICK SACCONE: That's it. Give it to them.

UNIDENTIFIED CROWD: (Chanting) CNN sucks. CNN sucks. CNN sucks.

SACCONE: Give it to them. They earned it. They earned it.

DETROW: Saccone praised the tax bill Trump recently signed into law, saying he would have voted for it.

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SACCONE: Not a single Democrat voted for that bill. And if Conor Lamb was there, he would have voted against it, too.

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DETROW: The argument boils down to if you like Trump, you need to vote for Saccone. Trump came to Pittsburgh to make it himself this weekend.

TRUMP: He's trying to act like a Republican so he gets - he won't give me one vote.

DETROW: Trump sounded confident Saturday, but tomorrow a district that favored him by nearly 20 points is in real danger of slipping into the Democratic column. Scott Detrow, NPR News, Pittsburgh. Transcript provided by NPR, Copyright NPR.